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MP task #47: DISPROVE the Entity-layout root cause; correct the record

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The prior commit (c78662a) filed cross-pod damage failure under a
"cross-TU Entity/EntityID layout divergence" (and the P5 base-region
audit). A compile-time offsetof probe injected into BOTH translation
units disproves that: game/reconstructed AND engine/MUNGA compute an
IDENTICAL Entity layout --

  sizeof(Entity)=444  offsetof(entityID)=380 (0x17C)
  offsetof(ownerID)=388  offsetof(simulationFlags)=32
  offsetof(Mech,entityID)=380  (Entity subobject at 0)

So Entity::Dispatch reads this->entityID at the SAME offset mech4's
GetEntityID() does -- there is no per-TU read difference, and the
logged 3:22 (mech4 candidate) vs 3:19 (engine Dispatch) cannot be one
object read two ways. Those lines were different objects/messages,
mis-correlated. The distinct, REAL P5 "base-region layout divergence"
(HARD_PROBLEMS.md) is about raw-offset stomps at this+0x2d4..0x2f0 --
far above entityID -- and is unrelated to #47.

Changes:
- Revert the committed BT_MP_NET engine diagnostics (ENTITY/EVENT/
  NTTMGR/RECEIVER/L4NET) to the clean a9c3e96 baseline -- those are
  the very instruments that produced the mis-correlated data.
- mech4 BT_MP_FORCE_DMG hook: dispatch via the real m->Dispatch(&td)
  path (no false id stamping); comment records the offsetof finding.
- context/multiplayer.md: layout-divergence RULED OUT; 3:22/3:19 marked
  unconfirmed; leading hypotheses reframed as H2 (wire host-relative
  (de)serialization) vs H3 (replicant id != master's registered key),
  to be distinguished by a 2-node run with per-message correlation.

Solo un-regressed (mech walks + targets, 0 faults). Cross-pod delivery
remains open, but the investigation is redirected off the wrong (large,
structural) layout-audit path onto the EntityID wire/id-assignment path.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
arcattack
2026-07-09 12:09:50 -05:00
co-authored by Claude Fable 5
parent c78662a0f1
commit 04a2049ce2
7 changed files with 55 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files
game/reconstructed/mech4.cpp
+18 -9
View File
@@ -2390,6 +2390,10 @@ void
static float s_candLog = 0.0f; s_candLog += dt;
const int candLog = (getenv("BT_MP_LOG") && s_candLog >= 1.0f);
if (candLog) s_candLog = 0.0f;
if (candLog)
DEBUG_STREAM << "[mp-self] MY mech entityID=" << GetEntityID()
<< " inst=" << (int)GetInstance() << " (" << nc << " candidates)\n"
<< std::flush;
if (candLog)
for (int ci = 0; ci < nc; ++ci)
{
@@ -2405,10 +2409,16 @@ void
<< " zones=" << m->damageZoneCount << "\n" << std::flush;
}
// CROSS-POD DAMAGE PROOF HOOK (BT_MP_FORCE_DMG, task #46): once a
// second, dispatch a real TakeDamage at the first live REPLICANT
// candidate -- isolating the Dispatch-reroute-to-owning-master path
// from the MP interactive aim/drive plumbing.
// CROSS-POD DAMAGE PROOF HOOK (BT_MP_FORCE_DMG, task #46/#47): once a
// second, dispatch a real unaimed TakeDamage at the first live
// REPLICANT candidate through the SAME engine path a beam hit uses
// (Entity::Dispatch -> replicant reroute -> SendMessage(ownerID)).
// This isolates the cross-pod delivery from the interactive aim/drive
// plumbing so a 2-node test can watch the wire without having to line
// up a boresight. It does NOT stamp/patch the id -- Entity::Dispatch
// reads this->entityID at offset 0x17C, which the [mp-layout] probe
// proved is IDENTICAL in the reconstructed and engine TUs (both 380,
// sizeof(Entity)=444), so no cross-TU translation is needed or done.
if (getenv("BT_MP_FORCE_DMG"))
{
static float s_fd = 0.0f; s_fd += dt;
@@ -2430,11 +2440,10 @@ void
Entity::TakeDamageMessageID,
sizeof(Entity::TakeDamageMessage),
GetEntityID(), -1, dmg);
DEBUG_STREAM << "[mp-force] PRE m->GetEntityID()=" << m->GetEntityID()
<< " td.entityID=" << td.entityID << "\n" << std::flush;
((Entity *)m)->Dispatch(&td);
DEBUG_STREAM << "[mp-force] POST td.entityID=" << td.entityID
<< " (== what Dispatch put on the wire)\n" << std::flush;
DEBUG_STREAM << "[mp-force] " << (void*)m
<< " Dispatch unaimed TakeDamage id=" << m->GetEntityID()
<< " ownerID=" << (int)m->GetOwnerID() << "\n" << std::flush;
m->Dispatch(&td);
break;
}
}